The present invention relates to a steel-producing installation, and more particularly to an arrangement for producing steel from scrap, sponge iron, pellets or similar materials.
There are already known various installations for producing steel from various starting materials, among them scrap, pellets or sponge iron and similar materials. The present invention is concerned with an arrangement of the latter type. It is well known that these substances constitute very valuable starting materials for production of steel. However, it is also already known that such materials cannot be used as such by being only melted and then cast into forms to constitute ingots. Rather, particularly since these materials contain large amounts of impurities, such as oxides, they must be refined by treating them in a furnace, such as an electric arc discharge furnace or an induction oven, by blowing or by similar methods of refining to obtain steel which then may be discharged from the furnace, after being rid of slag, and then used for useful purposes.
It has already been proposed to melt such materials in a melting vessel in such a manner that the starting materials are accommodated in the vessel to form a column of material in the vessel, the lowermost part of the column being subjected to heat generated by burning a combustible substance in the lowermost region of the column, by creating an electric discharge arc in such region, or by similar methods. In this arrangement, the heating arrangement melts the starting material and the molten material accumulates in the lowermost portion of the vessel to be discharged therefrom through a discharge opening located in the bottom portion of the vessel. An accumulating receptacle is then located underneath the discharge opening of the vessel and the molten material accumulates therein to be subsequently transported to and introduced into a conventional refining or similar converting furnace. This method and arrangement are very uneconomical, particularly since the molten material loses a substantial part of its heat content to the environment before it can be delivered to the furnace in which it is refined.
In order to avoid the above-mentioned drawback, it has also already been proposed to replace the accumulating receptacle by an electric induction or arc discharge oven which has an upper inlet opening communicating with the discharge opening of the melting vessel. In this prior-art arrangement, the oven is constructed as a flow-through container into which the starting material in its melted form is introduced on a continuous basis through the inlet opening of the container, while slag is separated from and separately but continuously discharged from the container through a slag outlet opening, while the steel which has been previously subjected to the necessary heat-treatment and which has been possibly supplemented with additives, is also continuously discharged from the container through a steel-outlet opening which is spaced from the outlet opening for slag. It is true that this arrangement avoids the above-mentioned disadvantage by directly communicating the outlet or discharge opening of the vessel with the inlet opening of the container or oven. However, since the oven works on a continuous basis, particularly as the steel-discharging part of the operation thereof is concerned, this results in a further disadvantage that the just refined steel discharged from the oven or furnace through the steel-discharge opening thereof must be accumulated in a receptacle, which takes up a relatively long period of time, particularly if the receptacle is of such dimensions which are of interest in steel-producing installations. The particular disadvantage of this arrangement is to be seen in the fact that the slowly accumulating refined steel in the receptacle dissipates a substantial part of its heat content into the ambient atmosphere and a not insubstantial amount of the heat content is also lost by convection and conduction. Thus, when the receptacle is full, the temperature thereof is not uniform in all regions thereof so that the steel must be subsequently heat-treated in order to homogenize the temperature throughout the body of steel accommodated in the receptacle. A further disadvantage of the continuous operation of the furnace and particularly of the continuous discharge of the steel therefrom is the fact that a full receptacle has to be replaced by an empty receptacle while further amounts of steel are being continuously discharged from the outlet opening for steel, which is a rather laborious if not dangerous operation.